1. Field of the Invention
This invention relates to hair-dyeing preparations based on oxidation dyes.
2. Statement of Related Art
Hair-dyeing preparations containing oxidation dye precursors dispersed in a cosmetic carrier are known in the art. The oxidation dye precursors present in such preparations are developer substances and coupler substances which form dyes under the effect of oxidizing agents or atmospheric oxygen. The cosmetic carriers used for the oxidation dye precursors include creams, emulsions, gels, shampoos, foam aerosols or other preparations suitable for application to the hair.
By virtue of their intense colors and good fastness properties, so-called oxidation hair dyes play a prominent part in the dyeing of hair. Oxidation dyes are formed by the oxidative coupling of one or more developer components with one another or with one or more coupler components. The developer substances commonly used are primary aromatic amines containing another free or substituted hydroxy or amino groups in the para position or ortho position, as well as diaminopyridine derivatives, heterocyclic hydrazone derivatives, 4-aminopyrazolone derivatives, and tetraaminopyrimidines. The so-called coupler substances commonly used are m-phenylenediamine derivatives, naphthols, resorcinol derivatives and pyrazolones.
Good oxidation dye precursors must satisfy certain primary requirements. They must form the desired shades of color with sufficient intensity during the oxidative coupling reaction. In addition, they must be readily absorbed by human hair without excessively staining the scalp. Dye absorption should also be uniform, i.e., the more heavily stressed ends should not be dyed to a greater extent than the less damaged hairline. The dye finishes produced using such precursors should be highly stable to heat, light and the chemicals used in the permanent waving of hair. Finally, the oxidation hair dye precursors should be safe to use from the toxicological and dermatological standpoint.
Aminodiphenylamines of a different chemical structure are known in the art as oxidation dye precursors, as disclosed for example in German patent document DE-PS 294 184 and in U.S. Pat. No. 4,200,432. However, the hair-dyeing preparations prepared with these products are unsatisfactory in regard to the fastness properties of the dye finishes obtained. In particular, these amoinodiphenylamines are not suitable as red couplers for developer components of the 2,4,5,6-tetraaminopyrimidine type either because they do not form red shades with developers of this type or because the shades formed are absorbed too unevenly. Also, these materials tend to color the hair ends to a greater extent than the less damaged, newer hairline regions closer to the hair roots. This disadvantage appears to be common to all known red couplers for developers of the tetraaminopyrimidine type.